Caddy is a production-grade, extensible web server platform written in Go. It automatically manages HTTPS certificates (via ACME/ZeroSSL) and provides a rich set of HTTP middleware including reverse proxy, file serving, authentication, compression, and headers manipulation. The architecture is modular: all features are registered as Caddy modules following a consistent lifecycle (Provision/Validate/Cleanup) and configured via a JSON config or the Caddyfile adapter. Key entry points are the CLI (caddy run, caddy start, etc.) and the admin API for runtime config changes. Primary data flows involve incoming HTTP requests being processed by a middleware chain of matchers and handlers, with TLS termination handled by the TLS app. External dependencies include certmagic for certificate management, zap for structured logging, Prometheus for metrics, and OpenTelemetry for tracing. The codebase is actively maintained with extensive test coverage and fuzz testing.
This repository is the curl project, consisting of the libcurl library and the curl command-line tool. libcurl is a client-side URL transfer library supporting a wide range of protocols including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, SMTP, POP3, IMAP, LDAP, MQTT, WebSocket, and many more. The curl tool provides a powerful command-line interface for making network requests with extensive options for authentication, SSL/TLS configuration, proxy support, output formatting, and scripting. The architecture is a classic C library with a public API (include/curl/) and a separate CLI tool (src/) that links against the library. Key entry points include curl_easy_perform() for synchronous transfers, curl_multi_perform() for asynchronous multiplexed transfers, and the curl command-line binary. Data flows involve URL parsing, DNS resolution (with support for c-ares, threaded, and DoH), connection establishment via a filter chain (TCP, TLS, HTTP/2, HTTP/3, SOCKS, etc.), protocol-specific handling, and response processing. External dependencies include OpenSSL, GnuTLS, wolfSSL, mbedTLS, Schannel, rustls for TLS; c-ares for async DNS; libssh2/libssh for SSH; nghttp2 for HTTP/2; ngtcp2 and quiche for HTTP/3; and various system libraries. The codebase is exceptionally well-structured, with a modular filter architecture, extensive test coverage (unit, integration, and HTTP test suites), and a strong emphasis on portability across Unix, Windows, macOS, and embedded platforms.
This repository is the source code for NGINX, a production-grade web server, reverse proxy, load balancer, API gateway, and mail proxy. The codebase is written entirely in C and is a definitive example of high-performance systems architecture. It employs a modular, event-driven, multi-process (master/worker) model. The core infrastructure is built around a set of highly optimized, self-contained data structures and utilities: a slab allocator for shared memory, a memory pool for request-scoped allocation, a red-black tree for timers and caches, a radix tree for IP routing, a hash table with wildcard support for server name matching, and an incremental JSON parser. The build system (auto/) is a sophisticated set of shell scripts that handle platform detection, dependency configuration, and module compilation. The code supports HTTP/1.x, HTTP/2, HTTP/3 (QUIC), TCP/UDP proxying (Stream module), and mail protocols (POP3, IMAP, SMTP). It is actively maintained, with a strong focus on performance, stability, and security. The code is exceptionally clean and well-structured for a project of its age and complexity, though it contains some platform-specific #ifdef sprawl and duplication between HTTP and Stream modules (e.g., upstream least_time, map).
Proxygen is a production-grade C++ HTTP library developed by Meta, providing comprehensive support for HTTP/1.1, HTTP/2, HTTP/3 (QUIC), and WebTransport. It offers both a classic callback-based server/client framework and a modern coroutine-based API using folly::coro. The architecture is layered: low-level codecs for wire protocol parsing, session management with flow control and rate limiting, transport abstraction (TCP, TLS, QUIC), and high-level handler/filter chains. The library includes extensive utilities for DNS resolution, consistent hashing, stream compression, structured headers, and connection pooling. It is heavily tested and designed for high-performance, multi-threaded production environments. While primarily a server framework, it also provides a full client stack and sample applications (echo, proxy, push, WebSocket, H3). The codebase is well-structured with many reusable components, though it remains tightly coupled to Meta's ecosystem (folly, wangle, fizz, mvfst).
webtransport-go is a Go library implementing the WebTransport protocol over HTTP/3, based on quic-go. It provides both client and server functionality to establish WebTransport sessions over QUIC connections, supporting bidirectional and unidirectional streams, datagrams, and session flow control. The library follows draft-ietf-webtrans-http3-16 and includes mechanisms for capsule-based control messages, stream error mapping, and origin checking. It is used in production by projects like Centrifugo, go-libp2p, and MediaMTX. The architecture is modular, with separate components for session management, stream maps, flow control, and capsule parsing. The server integrates with http3.Server via ConfigureHTTP3Server and provides an Upgrade method on HTTP handlers. The client offers both one-shot Dial and multi-session NewClientConn. The codebase emphasizes correctness with extensive unit and integration tests, including tests for reordering, flow control, and error handling. Key design decisions include the use of goroutines for concurrent stream acceptance and capsule processing, channel-based notification for flow control updates, and careful handling of session close to ensure streams are properly terminated. The implementation handles edge cases like stream reordering before session establishment, deadline propagation, and graceful shutdown with configurable timeouts. The repository is well-maintained with active CI, linting, and dependency management. It demonstrates strong Go engineering practices with clean interfaces, proper error handling, and comprehensive test coverage.
Apache Traffic Server is a high-performance HTTP/HTTPS forward and reverse proxy server with caching capabilities, used in production CDNs and large-scale web infrastructures. It handles HTTP/1.1, HTTP/2, HTTP/3 (over QUIC), and WebSocket connections, supporting TLS termination, URL rewriting, access control, and extensive logging. The architecture is event-driven and multi-threaded (thread-per-core design) with a plugin system that allows dynamic loading of C, Lua, and (deprecated) C++ plugins. Core subsystems include the event system (iocore/eventsystem), network I/O (iocore/net), cache (iocore/cache), HTTP state machine (proxy/http), DNS resolution (iocore/dns), logging (proxy/logging), and management RPC (mgmt/rpc). Configuration is primarily YAML-based, with legacy flat-file formats still supported. Key entry points are the main server binary (traffic_server), the management CLI (traffic_ctl), and log analysis tools (traffic_logcat, traffic_top). The primary data flow begins with client connection acceptance, proceeds through the HTTP state machine (HttpSM) which performs cache lookup, origin server connection (on miss), response processing, and logging. Plugins can hook into multiple transaction phases to modify headers, rewrite URLs, enforce access control, or transform content. External dependencies include OpenSSL (or BoringSSL/quictls), PCRE2, Lua, libxml2, libcurl, and compression libraries (zlib, brotli, zstd). Several third-party libraries are vendored in-tree (yamlcpp, Catch2, highway, swoc), which reduces external build complexity but introduces maintenance overhead.
Kwik is a pure Java implementation of the QUIC transport protocol (RFC 9000, RFC 9001, RFC 9369) supporting versions 1 and 2, along with extensions for unreliable datagrams (RFC 9221) and reliable stream reset. It provides both client and server APIs, with a modular architecture consisting of core protocol engine, CLI tool, HTTP/0.9 support, qlog structured logging, and interoperability test harness. The library is designed for embedding in Java applications needing low-latency, multiplexed, encrypted network connections. It includes a custom TLS 1.3 engine (agent15) for handshake management and leverages Java's module system. Extensive unit tests and interop testing against other QUIC implementations ensure protocol compliance. The codebase demonstrates strong engineering practices with clean abstractions (filter chains, builder patterns, null objects), though some features like server connection migration and stream priority remain incomplete.
This repository is a Go HTTP client library named 'req' (module github.com/imroc/req/v3). It provides a high-level, fluent API for making HTTP requests with extensive features including HTTP/1.1, HTTP/2, and HTTP/3 support, automatic retries with configurable backoff and conditions, middleware chains for request/response processing, TLS fingerprint impersonation (via uTLS), bandwidth rate limiting, parallel file downloads, digest authentication, and detailed debugging capabilities (dump, trace, curl command generation). The library is designed for production use, with a focus on ease of use and flexibility, allowing developers to build custom SDKs on top of it. The architecture centers around a Client struct that holds configuration and a Transport that wraps net/http with additional capabilities. Requests are built using a builder pattern (R() method) and executed via method-specific helpers (Get, Post, etc.). The codebase includes a significant amount of internal code forked from Go's standard library (HTTP/2, chunked encoding) and third-party dependencies (quic-go for HTTP/3, brotli, zstd). It is a pure application library with no data analysis or research components.
XQUIC is a production-grade C implementation of the QUIC transport protocol (RFC 9000) and HTTP/3 (RFC 9114), developed by Alibaba. It provides a full-featured QUIC stack including connection management, packet encryption, loss detection, congestion control (BBR, CUBIC, NewReno, Copa), and HTTP/3 with QPACK header compression. The library also supports experimental extensions such as Multipath QUIC, Forward Error Correction (FEC), and Media over QUIC (MoQ) for streaming media. The architecture is modular with a callback-driven engine, pluggable congestion control and TLS backends (BoringSSL, BabaSSL), and extensive testing infrastructure including unit tests (CUnit), integration shell scripts, and interoperability tests. The codebase is well-structured with reusable utility components (ring buffers, hash tables, object pools, timer managers) and demonstrates strong software engineering practices, though the large number of feature flags and experimental extensions introduce some complexity and potential drift.
This repository provides a Ring adapter for Jetty web servers, enabling Clojure/Ring applications to run on Jetty 11 and 12 with support for modern web protocols. Despite its 'jetty9' name, it tracks recent Jetty releases and adds features like HTTP/2, HTTP/3, and WebSocket support that aren't in the official Ring Jetty adapter. The architecture centers around a core adapter that creates and configures Jetty Server instances, with separate implementations for synchronous and asynchronous Ring handlers. It cleanly separates concerns: connection handling (HTTP/HTTPS/HTTP/2/HTTP/3), request/response translation between Jetty and Ring models, and protocol-specific upgrades (WebSocket). The adapter supports virtual threads, SSL/TLS configuration, and serves as a drop-in replacement for the official ring-jetty-adapter while offering more recent Jetty versions and additional features. Notable for its quality implementation are the WebSocket bridge that properly translates between Jetty's WebSocketListener and Ring's WebSocket protocols, and the asynchronous handler implementation that correctly manages the race condition between handler completion and timeout using atomic state and Jetty's scheduling facilities. The optional HTTP/2 and HTTP/3 modules demonstrate good practices for extending the core adapter with dynamically loaded dependencies.
This is the official W3C WebTransport specification repository. It defines a JavaScript API for bidirectional, multiplexed network communication over QUIC and HTTP/3, providing reliable streams and unreliable datagrams. The repository contains the spec source in Bikeshed format (index.bs), supporting documents (explainer, use-cases, security questionnaire), and functional sample implementations (echo client/server and a WebCodecs-based video streaming demo). The core deliverable is the specification, while the samples serve as proof-of-concept implementations. The codebase is a hybrid: primarily a standards document, but includes runnable demo applications that illustrate the API usage patterns. The spec is still in early draft stage and references evolving IETF protocols.
This repository provides an HTTP/3 codec implementation for Netty, including QPACK header compression, frame encoding/decoding, and control stream handling. It is a library that integrates into Netty's channel pipeline to support HTTP/3 over QUIC. The codebase is well-structured, with extensive tests and reusable components like Huffman decoders, dynamic table management, and frame validation handlers. However, the repository has been archived and its work merged into the main Netty 4.2 branch, meaning it is no longer actively maintained. The code is mature but may be outdated relative to the latest Netty versions and RFC updates.